Yieldable mine roof support

ABSTRACT

A mine roof support includes a rigid body having a first end and a second end and defining an interior space, a cementitious material positioned within the interior space of the body and a plurality of support members extending circumferentially around the body and engaging an outer surface of the body. A method includes providing a mine roof support comprising a rigid body having a first end and a second end, a cementitious material positioned within an interior space defined by the body, and a support member extending circumferentially around the body and engaging an outer surface of the body. The method also includes selecting a load capacity and elongation value of the support member to provide controlled yieldable confinement of the mine roof support during loading of the mine roof support.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No. 61/659,758, filed Jun. 14, 2012, the entire content of which is hereby incorporated by reference.

BACKGROUND OF THE INVENTION

This invention is related to a mine roof support and, more particularly, to a yieldable mine roof support formed from a pipe that receives cementitious material.

Cribbing is frequently used to provide support in underground mine openings. One type of cribbing is formed using a standard corrugated culvert pipe that is filled with a cementitious material that is allowed to cure such that the pipe becomes a load-bearing structure. The culvert pipe is typically formed from 16 gauge galvanized steel sheet that is helically wound and joined along a continuous seam. When the corrugated pipe support is placed under a load, however, the corrugated pipe will eventually begin to separate along the continuous seam as the load and deformation of the pipe increases. The separation of the continuous seam typically results in a loss of confinement, thereby reducing the load-carrying capacity of the support.

SUMMARY OF THE INVENTION

In accordance with an aspect of the invention, a mine roof support includes a rigid, generally circular body having a first end and a second end, an outer surface, and an inner surface defining an interior space. The mine roof support also includes a support member extending circumferentially around the body and engaging an outer surface of the body.

In accordance with another aspect of the invention, a mine roof support includes a rigid body having a first end and a second end and defining an interior space, a cementitious material positioned within the interior space of the body and a plurality of support members extending circumferentially around the body and engaging an outer surface of the body.

In accordance with another aspect of the invention, a method includes providing a mine roof support comprising a rigid body having a first end and a second end, a cementitious material positioned within an interior space defined by the body, and a support member extending circumferentially around the body and engaging an outer surface of the body. The method also includes selecting a load capacity and elongation value of the support member to provide controlled yieldable confinement of the mine roof support during loading of the mine roof support.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an elevational view of a mine support, in accordance with an aspect of the invention.

FIG. 2 is a cross-sectional view of the mine support shown in FIG. 1, in accordance with an aspect of the invention.

FIG. 3 is a graph of testing results of mine supports showing load versus deflection, in accordance with an aspect of the invention.

FIG. 4 is an elevational view of another mine support, in accordance with an aspect of the invention.

FIG. 5 is an elevational view of n additional mine support, in accordance with an aspect of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention will now be described with reference to the accompanying figures. For purposes of the description hereinafter, the terms “upper”, “lower”, “right”, “left”, “vertical”, “horizontal”, “top”, “bottom”, and derivatives thereof shall relate to the invention as it is oriented in the drawing figures. However, it is to be understood that the invention may assume various alternative variations and step sequences, except where expressly specified to the contrary. It is to be understood that the specific apparatus illustrated in the attached figures and described in the following specification is simply an exemplary embodiment of the present invention. Hence, specific dimensions and other physical characteristics related to the embodiments disclosed herein are not to be considered as limiting.

Referring to FIGS. 1 and 2, one aspect of a mine support 10 includes a rigid body 12 having a first end 14 and a second end 16, and defining an interior space 18. The body 12 is generally cylindrical and includes an inner surface 20 and an outer surface 22. In one aspect, the body 12 may be, for example, a corrugated metal pipe formed from 16 gauge galvanized steel sheet that is helically wound and joined along a continuous seam (seam not shown), although other suitable arrangements for the body 12 may be utilized such as, for example, bright steel pipe (uncorrugated) or tubing of suitable dimensions.

The mine support 10 further includes a support member 26 that extends circumferentially around the body 12 and is configure to contact or engage the outer surface 22 of the body 12. As shown in FIG. 1, the mine support 10 includes three support members 26 spaced from each other and generally positioned adjacent to the second end 16 of the body 12. The mine support 10, however, may include one or more support members 26. The one or more support members 26 may also be positioned at the first end 14 of the body 12, the second end 16 of the body 12, or any position intermediate the first and second ends 14, 16 of the body 12.

The support member 26 may be formed from a polyester fabric strap that is positioned around and in contact with or engaged with the outer surface 22 of the body 12. The polyester fabric strap may have, for example, a 4,000 lbf peak load and have generally high elongation properties, such as, for example, 14% elongation at 4,000 lbf load.

The support member 26 may also be formed from a metal material, such as, for example, a steel strap, such as in the form of a steel pallet strap, having, for example, a 3,000 lbf peak load and generally low elongation properties. In one aspect, a steel pallet strap having 3% elongation at 12,000 lbf load.

Accordingly, the support member 26 may be formed from a strap of material having, in one example, a first end 27 and a second end 29, with the first end 27 secured to the strap or the second end 29 via any suitable fastening element 31. The support member 26 may also be provided as a single piece of material extending from the first end 14 to the second end 16 of the body 12. In one aspect, the support members 26 may have a width W of 2-5 inches. Other suitable support members 26 may also be utilized having various dimensions, configurations, and physical properties.

Referring again to FIGS. 1 and 2, in use, the second end 16 of the body 12 is engaged with a roof portion 30 of a mine opening 32, and the first end 14 of the body 12 is engaged with a floor portion 34 of the mine opening 32. A cementitious material 36 is received and contained within the interior space 18 of the body 12. The mine support 10 may be installed as a completed unit, with the body 12, support member 26, and cementitious material 36 forming an integral support that is positioned within the mine opening 32. The mine support 10 may also be installed as separate components. The cementitious material 36 may be aerated cementitious filler having a strength between 200-900 psi, although other suitable cementitious materials may be utilized. In one aspect, the cementitious material 36 has a strength of 350-400 psi.

Under loading and vertical displacement of the mine support 10, the support member 26 is placed under load and increases the confinement of the cementitious material 36, thereby increasing peak load and residual loads. In particular, the support member 26 substantially minimizes the degree to which the body 12 separates along its continuous seam and increases confinement by minimizing the amount of fractured cementitious material 36 from leaving the body 12. Thus, the mine roof support 10 has improved peak load and residual loading compared to conventional mine roof supports. Further, specific load capacity and elongation values of the support member 26 may be selected to optimize the performance of the mine support 10. As the mine support 10 undergoes deformation, the body 12 will start to separate along its continuous seam which is contained by the support member 26. The elongation value of the support member 26 will affect the degree to which the cementitious material 36 and body 12 will deform outward and the degree to which the seam of the body 12 will separate. Accordingly, the support member 26 along with the body 12 provides for controlled yieldable confinement, which may be optimized by selecting the load capacity and elongation values of the support member 26 alone or in combination with the load capacity and/or elongation value (or other physical properties) of the body 12. The circumference of the body 12 may expand upon loading in addition to elongation of the support members 26.

Referring to FIG. 3, mine supports 10 according to two embodiments of the present invention were tested along with a control. “Test A” tested a mine roof support 10, as described above, with a single support member 26 formed from polyester fabric placed one foot below the second end of the body. After 7 inches of deformation, the support member 26 broke, resulting in a sudden loss of confinement and its supporting capacity, as indicated at point “X” on the curve for Test A. “Test B” tested a mine roof support 10, as described above, with three spaced-apart support members 26 formed from steel straps having a 3,000 lbf peak load. As the mine roof support 10 was loaded, the three support members 26 broke during different points of deformation, which resulted in higher peak and residual loads. The three straps broke at points #1, #2, and #3 on the Test B curve. The support in Test C included no confinement bands or support members 26. It should be appreciated that prior to breakage of the support members 26 in Tests A and B, the supports thereof exhibited continued increased loading and 50-100% greater load than the support of Test C. In addition, after breakage of the support member in Test B and of all the support members in Test A, the performances of the mine supports A and B were similar to that of mine support C. These tests demonstrated that the performance of a conventional mine roof support can be manipulated through the use of one or more support members 26. By adjusting the type and number of support members 26, the performance of the mine roof support 10 can be tuned to achieve a specific response curve. The support member 26 may be formed from a number of different straps having various load-carrying capacities and elongation properties to assist in fine tuning the performance curve.

In one aspect of the invention, the mine support 10 provides sequential confinement thereof. The body 12 may bulge or otherwise yield followed by yielding of the support members 26, or support members 26 may yield first followed by yielding of the body 12. It has been found that the mine support 10 can exhibit at least 25% reduction in height upon loading without failure.

FIG. 4 illustrates an additional mine support 110, in accordance with another aspect of the invention. Mine support 110 includes a rigid body 112 having a first end 114 and a second end 116, and defining an interior space 118. The body 112 is generally cylindrical and extends along a longitudinal axis A-A and includes an inner surface 120 and an outer surface 122. In one aspect, the rigid body 112 may be, for example, any suitable material having sufficient mechanical properties for supporting a cementitous material in the interior space 118. In another aspect, the outer surface 122 may be generally smooth as illustrated in FIG. 4.

The mine support 110 further includes a plurality of support members 126 that extend circumferentially around the body 112 and configured to contact or engage the outer surface 122 of the body 112. As shown in FIG. 4, the mine support 110 includes four support members 126 spaced apart from each other and generally positioned along the length of the body 112. In one aspect, the support members 126 extend horizontally about the body 112, e.g. generally horizontal with respect to the roof portion 30 and/or the floor portion 34 or generally perpendicular with respect to the longitudinal axis A-A.

FIG. 5 illustrates an additional mine support 210, in accordance with another aspect of the invention. Mine support 210 includes a rigid body 212 having a first end 214 and a second end 216, and defining an interior space 218. The body 212 is generally cylindrical and extends along a longitudinal axis A-A and includes an inner surface 120 and an outer surface 222. In one aspect, the rigid body 212 may be, for example, any suitable material having sufficient mechanical properties for supporting a cementitous material in the interior space 218. In another aspect, the outer surface 222 may be generally smooth as illustrated in FIG. 5.

The mine support 210 further includes a continuous support member 226 that extends circumferentially around the body 212 and configured to contact or engage the outer surface 222 of the body 212. As shown in FIG. 2, the support member 226 is configured to be spaced apart generally positioned along the length of the body 212. In one aspect, the support member 226 extends angularly or helically about the body 212, e.g. generally angularly or helical with respect to the roof portion 30 and/or the floor portion 34 or generally angularly or helical with respect to the longitudinal axis A-A.

While several aspects of the invention were described in the foregoing detailed description, those skilled in the art may make modifications and alterations to these aspects without departing from the scope and spirit of the invention. Accordingly, the foregoing description is intended to be illustrative rather than restrictive. 

What is claimed is:
 1. A mine roof support, comprising: a rigid, generally circular body having a first end and a second end, an outer surface, and an inner surface defining an interior space; and a support member extending circumferentially around the body and engaging an outer surface of the body.
 2. The mine roof support of claim 1, further including a cementitious material positioned within the interior space of the body, wherein the cementitious material has a strength in the range of about 200 psi to about 900 psi.
 3. The mine roof support of claim 1, further including additional support members extending circumferentially around the body.
 4. The mine roof support of claim 3, wherein the support members are spaced apart along the body.
 5. The mine roof support of claim 1, wherein the support member extends horizontally about the body.
 6. The mine roof support of claim 1, wherein the support member extends helically about the body.
 7. The mine roof support of claim 1, wherein the support member is formed of a polyester material or a metal material.
 8. The mine roof support of claim 1, wherein the body is generally cylindrical.
 9. The mine roof support of claim 1, wherein the support member has a width in the range of about 2 inches to about 5 inches.
 10. A mine roof support, comprising: a rigid body having a first end and a second end, and defining an interior space; a cementitious material positioned within the interior space of the body; and a plurality of support members extending circumferentially around the body and engaging an outer surface of the body.
 11. The mine roof support of claim 10, further including additional support members extending circumferentially around the body.
 12. The mine roof support of claim 11, wherein the support members are spaced apart along the body.
 13. The mine roof support of claim 1, wherein the support member extends horizontally about the body.
 14. The mine roof support of claim 1, wherein the support member extends helically about the body.
 15. The mine roof support of claim 1, wherein the support member is formed of a polyester material or a metal material.
 16. The mine roof support of claim 1, wherein the body is generally cylindrical.
 17. The mine roof support of claim 1, wherein the support member has a width in the range of about 2 inches to about 5 inches.
 18. The mine roof support of claim 1, wherein the cementitious material has a strength in the range of about 200 psi to about 900 psi.
 19. A method comprising: providing a mine roof support comprising a rigid body having a first end and a second end, a cementitious material positioned within an interior space defined by the body, and a support member extending circumferentially around the body and engaging an outer surface of the body; and selecting a load capacity and elongation value of the support member to provide controlled yieldable confinement of the mine roof support during loading of the mine roof support.
 20. The method of claim 19, further including: providing additional support members extending circumferentially around the body; and spacing the support members along a length of the body. 